Actinium Presents ATNM-400 Breast Cancer Data, Demonstrating Strong Anti-Tumor Activity
- Strong Anti-Tumor Activity: ATNM-400 demonstrated significant tumor growth inhibition across various breast cancer models, particularly in hormone receptor-positive and triple-negative cases, with all treatment regimens well tolerated and no significant body weight changes observed, indicating its potential clinical value.
- Effectiveness Against Resistant Tumors: The drug induced irreversible DNA damage in standard treatment-resistant breast cancer models, showcasing its unique advantage in addressing resistant tumors and potentially offering new treatment options for patients.
- Broad Applicability: ATNM-400 not only shows strong efficacy in breast cancer but also exhibits promising anti-tumor activity in prostate cancer and non-small cell lung cancer, supporting its potential as a targeted radiotherapy for multiple solid tumors.
- Market Demand Alignment: With an estimated increase to 250,000 women living with metastatic breast cancer by 2030, the development of ATNM-400 aligns perfectly with this growing market need, potentially providing new hope for patients with hard-to-treat breast cancer.
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- Strong Anti-Tumor Activity: ATNM-400 demonstrated significant tumor growth inhibition across various breast cancer models, particularly in hormone receptor-positive and triple-negative cases, with all treatment regimens well tolerated and no significant body weight changes observed, indicating its potential clinical value.
- Effectiveness Against Resistant Tumors: The drug induced irreversible DNA damage in standard treatment-resistant breast cancer models, showcasing its unique advantage in addressing resistant tumors and potentially offering new treatment options for patients.
- Broad Applicability: ATNM-400 not only shows strong efficacy in breast cancer but also exhibits promising anti-tumor activity in prostate cancer and non-small cell lung cancer, supporting its potential as a targeted radiotherapy for multiple solid tumors.
- Market Demand Alignment: With an estimated increase to 250,000 women living with metastatic breast cancer by 2030, the development of ATNM-400 aligns perfectly with this growing market need, potentially providing new hope for patients with hard-to-treat breast cancer.
- Potent Anti-Tumor Activity: ATNM-400 demonstrated significant tumor growth inhibition across various breast cancer models, particularly in hormone receptor-positive and triple-negative types, with all treatment regimens well tolerated and no significant weight changes observed, indicating its potential for clinical application.
- Efficacy in Resistant Models: In trastuzumab- and tamoxifen-resistant breast cancer cells, ATNM-400 exhibited enhanced cytotoxicity, and combining it with standard treatments resulted in greater cytotoxicity and tumor regression, showcasing its promise as a combination therapy.
- Mechanistic Evidence of DNA Damage: Treatment with ATNM-400 led to irreversible double-strand DNA breaks in breast cancer cells, activating AKT phosphorylation, which indicates its effective mechanism in resistant models and may provide new options for treating hard-to-treat breast cancer.
- Broad Applicability: Beyond breast cancer, ATNM-400 has shown potential efficacy in prostate cancer and non-small cell lung cancer, supporting its development as a multi-indication targeted radiotherapy to meet clinical needs.

New Treatment for Resistant Cancers: Actinium Pharmaceuticals announced promising preclinical data for ATNM-400, an antibody radioconjugate showing anti-tumor activity in hormone-resistant and HER2-resistant breast cancer, as well as efficacy in prostate and non-small cell lung cancers.
Presentation at SABCS: The data will be presented at the 2025 San Antonio Breast Cancer Symposium, highlighting ATNM-400's potential to overcome resistance to standard therapies like tamoxifen and trastuzumab, and its ability to synergize with existing treatments.
Broad Indication Potential: ATNM-400 demonstrates best-in-class efficacy across multiple solid tumors, with significant opportunities in high-value markets, including prostate cancer and NSCLC, where it has shown superior activity compared to leading therapies.
Innovative Mechanism: Utilizing Actinium-225, ATNM-400 targets a disease-driving protein linked to poor prognosis, offering a novel approach that may improve outcomes for patients with difficult-to-treat cancers, addressing significant unmet clinical needs.

ATNM-400 Overview: Actinium Pharmaceuticals' ATNM-400 is a first-in-class antibody radioconjugate targeting a non-PSMA antigen, demonstrating potent anti-tumor activity and prolonged survival in prostate cancer models resistant to standard therapies like enzalutamide and 177Lu-PSMA-617.
Efficacy and Resistance: Preclinical studies show that ATNM-400 outperforms existing treatments, achieving durable tumor control and complete regression in 40% of cases when combined with enzalutamide, highlighting its potential in overcoming treatment resistance.
Clinical Implications: The novel mechanism of ATNM-400 offers a promising alternative for patients with metastatic castration-resistant prostate cancer (mCRPC) who have limited options due to low or absent PSMA expression, addressing a significant unmet clinical need.
Future Directions: Actinium plans to explore ATNM-400's applications beyond prostate cancer, including non-small cell lung cancer (NSCLC), where it has shown potential to overcome resistance to existing therapies, further expanding its therapeutic impact.







